US20230045245A1 - Heterocyclic compound or salt thereof, active material, electrolytic solution and redox flow battery - Google Patents

Heterocyclic compound or salt thereof, active material, electrolytic solution and redox flow battery Download PDF

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US20230045245A1
US20230045245A1 US17/933,599 US202217933599A US2023045245A1 US 20230045245 A1 US20230045245 A1 US 20230045245A1 US 202217933599 A US202217933599 A US 202217933599A US 2023045245 A1 US2023045245 A1 US 2023045245A1
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electrolytic solution
formula
group
redox flow
flow battery
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Atsushi KAIHO
Shinya Nagatsuka
Tomoya NAKAJIMA
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Nippon Kayaku Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184—Regeneration by electrochemical means
    • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C309/00—Sulfonic acids; Halides, esters, or anhydrides thereof
    • C07C309/01—Sulfonic acids
    • C07C309/02—Sulfonic acids having sulfo groups bound to acyclic carbon atoms
    • C07C309/03—Sulfonic acids having sulfo groups bound to acyclic carbon atoms of an acyclic saturated carbon skeleton
    • C07C309/07—Sulfonic acids having sulfo groups bound to acyclic carbon atoms of an acyclic saturated carbon skeleton containing oxygen atoms bound to the carbon skeleton
    • C07C309/09—Sulfonic acids having sulfo groups bound to acyclic carbon atoms of an acyclic saturated carbon skeleton containing oxygen atoms bound to the carbon skeleton containing etherified hydroxy groups bound to the carbon skeleton
    • C07C309/11—Sulfonic acids having sulfo groups bound to acyclic carbon atoms of an acyclic saturated carbon skeleton containing oxygen atoms bound to the carbon skeleton containing etherified hydroxy groups bound to the carbon skeleton with the oxygen atom of at least one of the etherified hydroxy groups further bound to a carbon atom of a six-membered aromatic ring
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C323/00—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups
    • C07C323/64—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and sulfur atoms, not being part of thio groups, bound to the same carbon skeleton
    • C07C323/66—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and sulfur atoms, not being part of thio groups, bound to the same carbon skeleton containing sulfur atoms of sulfo, esterified sulfo or halosulfonyl groups, bound to the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C49/00—Ketones; Ketenes; Dimeric ketenes; Ketonic chelates
    • C07C49/587—Unsaturated compounds containing a keto groups being part of a ring
    • C07C49/753—Unsaturated compounds containing a keto groups being part of a ring containing ether groups, groups, groups, or groups
    • C07C49/755—Unsaturated compounds containing a keto groups being part of a ring containing ether groups, groups, groups, or groups a keto group being part of a condensed ring system with two or three rings, at least one ring being a six-membered aromatic ring
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C59/00—Compounds having carboxyl groups bound to acyclic carbon atoms and containing any of the groups OH, O—metal, —CHO, keto, ether, groups, groups, or groups
    • C07C59/40—Unsaturated compounds
    • C07C59/58—Unsaturated compounds containing ether groups, groups, groups, or groups
    • C07C59/64—Unsaturated compounds containing ether groups, groups, groups, or groups containing six-membered aromatic rings
    • C07C59/66—Unsaturated compounds containing ether groups, groups, groups, or groups containing six-membered aromatic rings the non-carboxylic part of the ether containing six-membered aromatic rings
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D241/00—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings
    • C07D241/36—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings condensed with carbocyclic rings or ring systems
    • C07D241/38—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings condensed with carbocyclic rings or ring systems with only hydrogen or carbon atoms directly attached to the ring nitrogen atoms
    • C07D241/46—Phenazines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/08—Fuel cells with aqueous electrolytes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2602/00—Systems containing two condensed rings
    • C07C2602/02—Systems containing two condensed rings the rings having only two atoms in common
    • C07C2602/14—All rings being cycloaliphatic
    • C07C2602/26—All rings being cycloaliphatic the ring system containing ten carbon atoms
    • C07C2602/28—Hydrogenated naphthalenes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2603/00—Systems containing at least three condensed rings
    • C07C2603/02—Ortho- or ortho- and peri-condensed systems
    • C07C2603/04—Ortho- or ortho- and peri-condensed systems containing three rings
    • C07C2603/22—Ortho- or ortho- and peri-condensed systems containing three rings containing only six-membered rings
    • C07C2603/24—Anthracenes; Hydrogenated anthracenes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • H01M2300/0005—Acid electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present disclosure relates to a heterocyclic compound and a salt thereof.
  • the present disclosure also relates to an active material containing the heterocyclic compound or a salt thereof, an electrolytic solution containing the active material, and a redox flow battery including the electrolytic solution.
  • Electrolytic solutions of redox flow batteries which are expected to serve as large storage batteries include aqueous ones and nonaqueous ones, but aqueous electrolytic solutions are superior in the safety and the cost.
  • active materials are required to have a high solubility to water and in order to attain a high energy density, are desired to have a suitable oxidation reduction potential.
  • vanadium is used as an active material.
  • Use of vanadium has resource restrictions and the problem of fluctuation of the price (Jan Winsberg et al., Angew. Chem. Int. Ed. 2017, 56, 686-711, and P. Leung et al., Journal of Power Sources 360 (2017) 243-283).
  • active materials use of materials abundant as resources is desirable.
  • the present disclosure is related to providing a novel compound, an active material, an electrolytic solution and a redox flow battery which enable the improvement of the energy density and the cycle characteristic of the redox flow battery using an aqueous electrolyte solution.
  • a heterocyclic compound or a salt thereof according to an aspect of the present disclosure is represented by the following formula (1), (2) or (3):
  • R 1 to R 8 are each independently a hydrogen atom, an acidic group, an alkoxy group, an alkyl group, an amino group, an amide group or a group represented by formula (a), and at least one of R 1 to R 8 is a group represented by formula (a);
  • X 1 is an oxygen atom, a sulfur atom or NY 2 ;
  • Y 1 is a group represented by formula (b);
  • Y 2 is a hydrogen atom, an alkyl group, a carbonyl group, a sulfonyl group or a group represented by formula (b);
  • R 9 and R 10 each independently represent a hydrogen atom or a substituent;
  • Z 1 is an acidic group;
  • n represents an integer of 1 to 7;
  • X 2 is an oxygen atom, a sulfur atom or NR′′; Y 2 is a linker; Z 2 is an acidic group; n 1 is an integer of 1 to 6; R 11 is a hydrogen atom or an alkyl group; each R 12 is independently an alkyl group or an acidic group; and n 2 is an integer of 0 to 5, and
  • X 3 is an oxygen atom or a sulfur atom
  • Y 3 is a linker
  • Z 3 is an acidic group
  • n 3 is an integer of 3 to 8
  • each R 13 is independently an alkyl group or an acidic group
  • n 4 is an integer of 0 to 5.
  • Z 1 in the above formula (b) is a sulfo group.
  • At least two of R 1 to R 8 in the above formula (1) are each a group represented by the above formula (a).
  • R 2 and R 3 in the above formula (1) are each a group represented by the above formula (a).
  • An active material according to an aspect of the present disclosure contains at least one heterocyclic compound or a salt thereof described above.
  • An electrolytic solution according to an aspect of the present disclosure contains the above active material.
  • the electrolytic solution is an electrolytic solution for a redox flow battery.
  • the content of water contained in the electrolytic solution is 1% by mass or higher and 99.99% by mass or lower.
  • the content of water contained in the electrolytic solution is 10% by mass or higher and 99% by mass or lower.
  • a redox flow battery according to an aspect of the present disclosure includes the above electrolytic solution.
  • the redox flow battery further includes an electrode and a membrane.
  • FIG. 1 is a charge/discharge curve diagram exhibited by a redox flow battery 1 fabricated in Example 4.
  • FIG. 2 is a charge/discharge curve diagram exhibited by a redox flow battery 2 fabricated in Example 5.
  • FIG. 3 is a charge/discharge curve diagram exhibited by a redox flow battery 3 fabricated in Example 6.
  • FIG. 4 is a charge/discharge curve diagram exhibited by a redox flow battery 4 fabricated in Example 9.
  • FIG. 5 is a charge/discharge curve diagram exhibited by a redox flow battery 5 fabricated in Example 12.
  • FIG. 6 is a charge/discharge curve diagram exhibited by a redox flow battery 6 fabricated in Example 13.
  • FIG. 7 is a charge/discharge curve diagram exhibited by a redox flow battery 7 fabricated in Example 15.
  • FIG. 8 is a charge/discharge curve diagram exhibited by a redox flow battery 8 fabricated in Example 22.
  • FIG. 9 is a charge/discharge curve diagram exhibited by a redox flow battery 9 fabricated in Example 23.
  • FIG. 10 is a charge/discharge curve diagram exhibited by a redox flow battery 10 fabricated in Example 24.
  • FIG. 11 is a charge/discharge curve diagram exhibited by a redox flow battery 11 fabricated in Example 25.
  • FIG. 12 is a charge/discharge curve diagram exhibited by a redox flow battery 12 fabricated in Example 26.
  • FIG. 13 is a charge/discharge curve diagram exhibited by a redox flow battery 13 fabricated in Example 27.
  • FIG. 14 is a charge/discharge curve diagram exhibited by a redox flow battery 14 fabricated in Comparative Example 1.
  • FIG. 15 is a charge/discharge curve diagram exhibited by a redox flow battery 15 fabricated in Comparative Example 2.
  • FIG. 16 is a charge/discharge curve diagram exhibited by a redox flow battery 16 fabricated in Comparative Example 3.
  • a heterocyclic compound according to the present embodiments is represented by the following formula (1), (2) or (3). That is, the heterocyclic compound is selected from the group consisting of phenazine-based compounds represented by the following formula (1), naphthoquinone-based compounds represented by the following formula (2) and anthraquinone-based compounds represented by the following formula (3).
  • the heterocyclic compound is selected from the group consisting of phenazine-based compounds represented by the following formula (1), naphthoquinone-based compounds represented by the following formula (2) and anthraquinone-based compounds represented by the following formula (3).
  • the salt may be, for example, an alkaline metal salt such as a lithium salt, a sodium salt or a potassium salt, an alkaline earth metal salt such as a calcium salt or an ammonium salt such as an ammonium salt and a tetramethylammonium salt.
  • an alkaline metal salt such as a lithium salt, a sodium salt or a potassium salt
  • an alkaline earth metal salt such as a calcium salt
  • an ammonium salt such as an ammonium salt and a tetramethylammonium salt.
  • these groups may be all free acids, all salts, or partially free acids (partially salts).
  • these salts may be ones of the same kind, or may be ones of different kinds.
  • R 1 to R 8 are each independently a hydrogen atom, an acidic group, an alkoxy group, an alkyl group, an amino group, an amide group or a group represented by the formula (a), and at least one of R 1 to R 8 is a group represented by the formula (a);
  • X 1 in the formula (a) is an oxygen atom, a sulfur atom or NY 2 ;
  • Y 1 is a group represented by the formula (b);
  • Y 2 is a hydrogen atom, an alkyl group, a carbonyl group, a sulfonyl group or a group represented by the formula (b);
  • R 9 and R 10 in the formula (b) each independently represent a hydrogen atom or a substituent;
  • Z 1 is an acidic group;
  • n is an integer of 1 to 7;
  • Examples of the acidic group include a sulfo group, a carboxy group, a phosphoric acid group and a hydroxy group, and a sulfo group is preferable. These acidic groups may be free acids or may form salts.
  • alkoxy group examples include a methoxy group, an ethoxy group, a n-propoxy group, an isopropoxy group, a n-butoxy group and a t-butoxy group.
  • amino group examples include an amino group (—NH 2 ), a methylamino group, a dimethylamino group, an ethylamino group and a diethylamino group, and an amino group and the like are preferable.
  • amide group examples include a formamide group, an acetoamide group, a benzamide group and a pivalamide group, and an acetoamide group and the like are preferable.
  • alkyl group examples include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group and a t-butyl group.
  • Examples of the carbonyl group include an acetyl group, a pivaloyl group and a benzoyl group, and an acetyl group and the like are preferable.
  • sulfonyl group examples include a methanesulfonyl group, a p-toluenesulfonyl group, an o-nitrobenzenesulfonyl group and a trifluoromethanesulfonyl group.
  • substituents examples include an alkyl group.
  • n is 1 to 6; being 1 to 3 is more preferable; being 1 or 2 is still more preferable; and being 2 is especially preferable.
  • R 1 to R 8 in the formula (1) are each a group represented by the above formula (a); and it is more preferable that R 2 and R 3 are each a group represented by the above formula (a). It is preferable that Z 1 in the formula (b) is a sulfo group.
  • R 2 is a group represented by the above formula (a);
  • R 3 is a group represented by the formula (a) or an acidic group;
  • R 6 is a hydrogen atom, an amide group, an amino group or an acidic group;
  • R 1 , R 4 , R 5 , R 7 and R 8 are each a hydrogen atom;
  • X 1 in the formula (a) is an oxygen atom;
  • R 9 and R 10 in the formula (b) are each a hydrogen atom; and
  • n is 2.
  • the phenazine-based compound represented by the formula (1) may be used singly in one kind, or may be used in a combination of two or more kinds. In the case of using by combining two or more kinds, the two or more kinds can be used concurrently in any proportion.
  • X 2 is an oxygen atom, a sulfur atom or NR 11 ; Y 2 is a linker; Z 2 is an acidic group; n 1 is an integer of 1 to 6; R′′ is a hydrogen atom or an alkyl group; each R 12 is independently an alkyl group or an acidic group; and n 2 is an integer of 0 to 5.
  • alkyl group examples include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group and a n-hexyl group, and these alkyl groups may further have a substituent such as a hydroxy group, a thiol group, an alkoxy group, an amino group or a nitrile group.
  • the linker represents a moiety that links X 2 and Z 2 in the formula (2) together, and examples thereof include alkylene moieties and an “(alkylene-oxygen atom) m -alkylene linking moiety”.
  • alkylene moieties examples include a methylene moiety (—CH 2 —), an ethylene moiety (—CH 2 CH 2 —), a propylene moiety (—CH 2 CH 2 CH 2 —), a butylene moiety (—CH 2 CH 2 CH 2 CH 2 —) and an isopropylene moiety (—CH(CH3)CH 2 —), and being a propylene moiety is preferable.
  • Examples of the “(alkylene-oxygen atom) m -alkylene linking moiety” include an ethoxyethyl moiety (—CH 2 CH 2 OCH 2 CH 2 —), a methoxyethyl moiety (—CH 2 OCH 2 CH 2 —) and —CH 2 CH 2 O—CH 2 CH 2 O—CH 2 CH 2 —.
  • Examples of the acidic group include a sulfo group, a carboxy group, a phosphoric acid group and a hydroxy group, and being a sulfo group or a carboxy group is preferable. These acidic groups may be free acids, or may form salts.
  • n 1 is 1 to 4; being 1 or 2 is more preferable; and being 2 is especially preferable.
  • each X 2 , each Y 2 and each Z 2 may be independently the same or different, respectively.
  • n 2 is 0 to 3; being 0 or 1 is more preferable; and being 0 is especially preferable.
  • each R 12 may be independently the same or different.
  • X 2 is a sulfur atom
  • Y 2 is a propylene moiety
  • Z 2 is an acidic group
  • n 1 is 2
  • n 2 is 0. That is, in the formula (2), it is preferable that no substituent is present on benzene rings in the naphthoquinone skeleton.
  • the naphthoquinone-based compound represented by the formula (2) may be used singly in one kind, or may be used in a combination of two or more kinds. In the case of using by combining two or more kinds, the two or more kinds can be used concurrently in any proportion.
  • X 3 is an oxygen atom or a sulfur atom
  • Y 3 is a linker
  • Z 3 is an acidic group
  • n 3 is an integer of 3 to 8
  • each R 13 is independently an alkyl group or an acidic group
  • n 4 is an integer of 0 to 5.
  • the linker, the acidic group and the alkyl group are the same as defined in the above formula (2), respectively.
  • X 3 is an oxygen atom, and it is preferable that n 3 is 3 to 6.
  • X 3 , each Y 3 and each Z 3 may be independently the same or different, respectively.
  • X 3 is an oxygen atom
  • Y 3 is a methylene moiety, a propylene moiety or —CH 2 CH 2 O—CH 2 CH 2 O—CH 2 CH 2 —
  • Z 3 is a sulfo group, a carboxy group or a hydroxy group
  • n 3 is 3, 4 or 6
  • n 4 is 0.
  • the anthraquinone-based compound represented by the formula (3) may further have R 13 as a substituent. It is preferable that R 13 is an acidic group; and being a hydroxy group is more preferable.
  • n 4 suffices if the sum of the number of n 3 and the number of n 4 is set to be 8 or less; and it is preferable that n 4 is 1 or 2; and it is especially preferable that n 4 is 2.
  • anthraquinone-based compound in which in the formula (3), X 3 is an oxygen atom, Y 3 is —CH 2 CH 2 O—CH 2 CH 2 O—CH 2 CH 2 —, Z 3 is a hydroxy group, n 3 is 4, R 13 is a hydroxy group, n 4 is 2, and X 3 are substituted on positions 1, 3, 5 and 7 of the anthraquinone skeleton, respectively, and R 13 are substituted on positions 2 and 6 thereof, respectively.
  • Such a compound is represented by the following formula (3′).
  • the anthraquinone-based compound represented by the formula (3) may be used singly in one kind, or may be used in a combination of two or more kinds. In the case of using by combining two or more kinds, the two or more kinds can be used concurrently in any proportion.
  • An active material according to the present embodiment contains at least one heterocyclic compound represented by the formula (1), (2) or (3) or a salt thereof.
  • an aqueous electrolytic solution for a redox flow battery containing such an active material the energy density and the cycle characteristic of the redox flow battery can be improved.
  • the active material may contain any one of these heterocyclic compounds, or may contain two or more kinds thereof.
  • the active material is an active material for an aqueous electrolytic solution; and it is especially preferable that the active material is used for an electrolytic solution for a redox flow battery as an active material for an aqueous electrolytic solution.
  • the active material contained in an electrolytic solution may be either one of a positive electrode active material and a negative electrode active material, but being a negative electrode active material is preferable.
  • An electrolytic solution according to the present embodiment contains the above-mentioned active material.
  • the electrolytic solution is an electrolytic solution for a redox flow battery.
  • the active material in the electrolytic solution the heterocyclic compounds represented by the formula (1), (2) and (3) may be contained singly in one kind, or may be contained in two or more kinds. In the case of using by combining two or more kinds of active material, the two or more kinds can be blended in any proportion. It is preferable that the content of the active material contained in the electrolytic solution is 1% by mass or higher and 99% by mass or lower; and being 3% by mass or higher and 70% by mass or lower is more preferable.
  • the electrolytic solution may further contain, other than the heterocyclic compounds represented by the formula (1), (2) and (3), optionally other compounds in the range of not impairing the effects of the present disclosure.
  • the electrolytic solution may contain water.
  • a water ion-exchange water, millipore water or the like can be used, and millipore water is preferable.
  • the content of water in the above electrolytic solution can optionally be set, being 1% by mass or higher and 99.9% by mass or lower is preferable; being 10% by mass or higher and 99% by mass or lower is more preferable; and being 75% by mass or higher and 95% by mass or lower is especially preferable.
  • the electrolytic solution contains, as the active material, a naphthoquinone-based compound represented by the formula (2) and/or an anthraquinone-based compound represented by the formula (3), that is, a quinone-based compound
  • a quinone-based compound having a solubility to water of higher than 0.07 mol/L it is preferable to contain a quinone-based compound having a solubility to water of higher than 0.07 mol/L; and it is more preferable that the solubility to water is 0.1 mol/L or higher and 5.0 mol/L or lower; being 0.15 mol/L or higher and 4.0 mol/L or lower is still more preferable; and being 0.18 mol/L or higher and 3.0 mol/L or lower is especially preferable.
  • the electrolytic solution may further contain an antifoaming agent.
  • the antifoaming agent include alcohols such as methanol, ethanol and propanol, ketones such as acetone and methyl ethyl ketone, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol and glycerol, and various kinds of commercially available antifoaming agents.
  • the antifoaming agent is an alcohol; and being ethanol is especially preferable.
  • the content of the antifoaming agent contained in the electrolytic solution is not especially limited, but it is preferable that the content is 0.1% by mass or higher and 10% by mass or lower with respect to the amount of water contained in the electrolytic solution; and being 0.5% by mass or higher and 8% by mass or lower is more preferable.
  • a redox flow battery includes the above-mentioned electrolytic solution. It is preferable that the redox flow battery further includes an electrode and a membrane.
  • the electrodes can be optionally selected and used as long as functioning as an electrode, but it is preferable to use, for example, a carbon felt, a carbon paper or a carbon cloth, and using a carbon felt is more preferable.
  • the membrane can be optionally selected and used as long as functioning as a membrane between electrodes, but it is preferable to use, for example, an ion-exchange membrane, a porous membrane or the like, and using an ion-exchange membrane is more preferable.
  • the same electrolytic solution may be used for a positive electrode and a negative electrode, or different electrolytic solutions may be used.
  • the electrolytic solution according to the present embodiment and a counter electrolytic solution are used in combination.
  • the electrolytic solution according to the present embodiment for the negative electrode side and a counter electrolytic solution for the positive electrode side, respectively, that is, to use the electrolytic solution according to the present embodiment as a negative electrode electrolytic solution and the counter electrolytic solution as a positive electrode electrolytic solution, respectively.
  • One of or both of the electrolytic solution and the counter electrolytic solution to be used for the redox flow battery may further contain an electrolyte.
  • an electrolyte there can be used, for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, lithium chloride, sodium chloride, potassium chloride, ammonium chloride, sulfuric acid, acetic acid, formic acid or hydrochloric acid; and preferable are potassium hydroxide and sodium chloride, and especially preferable is sodium chloride.
  • the counter electrolytic solution is not especially limited as long as being one functioning as a positive electrode; there can be used, for example, potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, ferrocene, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), lithium iodide, sodium iodide, potassium iodide, ammonium iodide or vanadium; and being a potassium ferrocyanide or sodium iodide aqueous solution is preferable, and being a sodium iodide aqueous solution is especially preferable.
  • the redox flow battery contains the electrolytic solution and optionally members including the counter electrolytic solution, the electrodes, the membrane, and the like, and in order to form the battery by using these members, as required, assembling members may further be used such as containers, sealants, screws and bipolar plates.
  • the electrolytic solution and the redox flow battery including the same according to the present embodiment which contain the above-mentioned active material, has high energy density and also excellent cycle characteristic.
  • a high energy density can be given to the redox flow battery using an aqueous electrolytic solution, and as compared with nonaqueous electrolytic solutions using organic solvents or the like as a solvent of the electrolytic solutions, the electrolytic solution is high in the safety, and is excellent in workability and the maintainability in fabrication of the redox flow battery, exchange of electrolytic solutions, and the like.
  • room temperature is a temperature in the range of 20° C. ⁇ 5° C.
  • the wet cake was dissolved in 70 parts of water; and then, 10 parts of a 25% sodium hydroxide aqueous solution was added; thereafter, the resultant was poured in 1.5 L of ethanol; and a deposited solid was filtration separated to thereby obtain a red wet cake.
  • the wet cake was vacuum dried at 80° C. to thereby obtain 34.8 parts of a heterocyclic compound of the present disclosure represented by the following formula (1-1).
  • the wet cake was dissolved in 300 parts of water; thereafter, the resultant was poured in 2.0 L of ethanol, and a deposited solid was filtration separated to thereby obtain a purple wet cake.
  • the wet cake was vacuum dried at 70° C. to thereby obtain 42.9 parts of a heterocyclic compound of the present disclosure represented by the following formula (1-2).
  • the heterocyclic compound represented by the formula (1-1) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L, to thereby fabricate a negative electrode electrolytic solution 1.
  • sodium ferrocyanide manufactured by Fujifilm Wako Pure Chemical Corp., content: 95% or higher
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 1 and positive electrode electrolytic solution 1 were used as electrolytic solutions, to thereby fabricate a redox flow battery 1.
  • the positive electrode electrolytic solution 1 and the negative electrode electrolytic solution 1 of the redox flow battery 1 were circulated by peristaltic pumps piped and connected to outsides of the battery; and a test was carried out by using a multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 1 and the negative electrode electrolytic solution 1 were 20 ml and 6 ml, respectively; and a charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.6 V and the lower limit voltage being set at 0.5 V.
  • FIG. 1 shows a charge/discharge curve until the fifth cycle of the redox flow battery 1. In the fifth cycle, the coulomb efficiency was 92%; the voltage efficiency, 89%; and the energy density, 0.90 Wh/L, thus attaining a good cycle characteristic.
  • the heterocyclic compound represented by the formula (1-2) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L, to thereby fabricate a negative electrode electrolytic solution 2.
  • sodium ferrocyanide manufactured by Fujifilm Wako Pure Chemical Corp., content: 95% or higher
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 2 and positive electrode electrolytic solution 2 were used as electrolytic solutions, to thereby fabricate a redox flow battery 2.
  • the positive electrode electrolytic solution 2 and the negative electrode electrolytic solution 2 of the redox flow battery 2 were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 2 and the negative electrode electrolytic solution 2 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.6 V and the lower limit voltage being set at 0.5 V.
  • FIG. 2 shows a charge/discharge curve until the fifth cycle of the redox flow battery 2. In the fifth cycle, the coulomb efficiency was 96%; the voltage efficiency, 89%; and the energy density, 1.02 Wh/L, thus attaining a good cycle characteristic.
  • the heterocyclic compound represented by the formula (1-3) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L, to thereby fabricate a negative electrode electrolytic solution 3.
  • sodium ferrocyanide manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • Fujifilm Wako Pure Chemical Corp., content: 95% or higher was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.2 mol/L, to thereby fabricate a positive electrode electrolytic solution 3.
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 3 and positive electrode electrolytic solution 3 were used as electrolytic solutions, to thereby fabricate a redox flow battery 3.
  • the positive electrode electrolytic solution 3 and the negative electrode electrolytic solution 3 of the redox flow battery 3 were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 3 and the negative electrode electrolytic solution 3 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.6 V.
  • FIG. 3 shows a charge/discharge curve until the fifth cycle of the redox flow battery 3. In the fifth cycle, the coulomb efficiency was 98%; the voltage efficiency, 88%; and the energy density, 0.57 Wh/L, thus attaining a good cycle characteristic.
  • the screw vial containing the electrolytic solution was capped and shaken for 30 s at a pace of 110 times/30 s so the vertical motion width as to become 15 cm, and allowed to stand still for 5 min; thereafter, there was measured the minimum value of the height of air bubbles from the liquid level on the wall surface.
  • Example 8 the case (Example 8) of adding no antifoaming agent indicated in Table 2, air bubbles remained, by adding an antifoaming agent, air bubbles disappeared.
  • the hyphen “-” in Table 2 indicates that there were no air bubbles and the height of air bubbles could not be measured.
  • the heterocyclic compound represented by the formula (1-1) was dissolved in a 6-wt % ethanol aqueous solution to attain 0.5 mol/L to thereby fabricate a negative electrode electrolytic solution 4.
  • sodium iodide manufactured by Junsei Chemical Co., Ltd., first grade
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 4 and positive electrode electrolytic solution 4 were used as electrolytic solutions, to thereby fabricate a redox flow battery 4.
  • the positive electrode electrolytic solution 4 and the negative electrode electrolytic solution 4 of the redox flow battery 4 obtained above were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 4 and the negative electrode electrolytic solution 4 were 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 420 mA and with the upper limit voltage being set at 1.7 V and the lower limit voltage being set at 0.3 V.
  • FIG. 4 shows a charge/discharge curve until the second cycle of the redox flow battery 4. In the second cycle, the coulomb efficiency was 97%; the voltage efficiency, 66%; and the energy density, 8.92 Wh/L, thus attaining a good cycle characteristic.
  • the reaction liquid was cooled down to room temperature; 9.6 parts of a 25% sodium hydroxide aqueous solution was dropwise added and stirred for 1 hour; and the resultant was poured in 500 mL of acetone. A red wet cake was obtained by filtration separation, and washed with acetone. The wet cake was dissolved in 80 parts of water, and poured in 1.0 L of ethanol, and then, a deposited solid was filtered off and washed with ethanol to thereby obtain a brown wet cake, which was then further vacuum dried at 80° C. to thereby obtain 2.7 parts of a heterocyclic compound of the present disclosure represented by the following formula (1-5).
  • the heterocyclic compound represented by the formula (1-4) was dissolved in a sodium hydroxide (manufactured by Kokusan Chemical Co., Ltd., content: 97.0%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 5.
  • sodium ferrocyanide manufactured by Fujifilm Wako Pure Chemical Corp., content: 95% or higher
  • a sodium hydroxide manufactured by Kokusan Chemical Co., Ltd., content: 97.0%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 5 and positive electrode electrolytic solution 5 were used as electrolytic solutions, to thereby fabricate a redox flow battery 5.
  • the positive electrode electrolytic solution 5 and the negative electrode electrolytic solution 5 of the redox flow battery 5 were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 5 and the negative electrode electrolytic solution 5 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.6 V and the lower limit voltage being set at 0.5 V.
  • FIG. 5 shows a charge/discharge curve until the fifth cycle of the redox flow battery 5.
  • the coulomb efficiency was 81%; the voltage efficiency, 88%; and the energy density, 0.59 Wh/L, thus attaining a good cycle characteristic.
  • the heterocyclic compound represented by the formula (1-5) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L, to thereby fabricate a negative electrode electrolytic solution 6.
  • sodium ferrocyanide manufactured by Fujifilm Wako Pure Chemical Corp., content: 95% or higher
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 6 and positive electrode electrolytic solution 6 were used as electrolytic solutions, to thereby fabricate a redox flow battery 6.
  • the positive electrode electrolytic solution 6 and the negative electrode electrolytic solution 6 of the redox flow battery 6 were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 6 and the negative electrode electrolytic solution 6 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.5 V.
  • FIG. 6 shows a charge/discharge curve until the fifth cycle of the redox flow battery 6. In the fifth cycle, the coulomb efficiency was 89%; the voltage efficiency, 81%; and the energy density, 0.98 Wh/L, thus attaining a good cycle characteristic.
  • the wet cake was dissolved in 50 parts of water, and poured in 500 mL of 2-propanol, and then, a deposited solid was filtered off and washed with ethanol to thereby obtain a brown wet cake, which was then vacuum dried at 80° C. to thereby obtain 1.4 parts of a brown powder containing a heterocyclic compound of the present disclosure represented by the following formula (1-6).
  • the heterocyclic compound represented by the formula (1-6) was dissolved in a sodium hydroxide (manufactured by Kokusan Chemical Co., Ltd., content: 97.0%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 7.
  • sodium ferrocyanide manufactured by Fujifilm Wako Pure Chemical Corp., content: 95% or higher
  • a sodium hydroxide manufactured by Kokusan Chemical Co., Ltd., content: 97.0%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the above negative electrode electrolytic solution 7 and positive electrode electrolytic solution 7 were used as electrolytic solutions, to thereby fabricate a redox flow battery 7.
  • the positive electrode electrolytic solution 7 and the negative electrode electrolytic solution 7 of the redox flow battery 7 were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 7 and the negative electrode electrolytic solution 7 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.6 V and the lower limit voltage being set at 0.5 V.
  • FIG. 7 shows a charge/discharge curve until the fifth cycle. In the fifth cycle, the coulomb efficiency was 86%; the voltage efficiency, 91%; and the energy density, 0.83 Wh/L, thus attaining a good cycle characteristic.
  • Example 7 As indicated in the above Tables 1, 3, 4 and 5 and FIGS. 1 to 7 , it is clear that the redox flow batteries 1 to 7 fabricated in Examples 4 to 6, 9, 12, 13 and 15 had a high average discharge voltage (V) and a high energy density, and had a good cycle characteristic. Further it can be confirmed that in Example 7 in which ethanol was added as an antifoaming agent in the electrolytic solution, no generation of air bubbles occurred and the electrolytic solution was excellent in handleability.
  • Example 15 The same operation as in Example 15 was carried out, except for using 20.5 parts of bromoacetic acid in place of 20 parts of propane sultone and using potassium hydroxide in place of sodium hydroxide, to thereby obtain 7.9 parts of a heterocyclic compound of the present disclosure represented by the following formula (3-2).
  • the wet cake was little by little added in 150 parts of 5% sodium hydrogencarbonate aqueous solution; and after the stirring for 1 hour, the resultant suspension was subjected to filtration separation to thereby obtain a wet cake.
  • the wet cake was dried in a hot-air dryer at 80° C. to thereby obtain 13.1 parts of a compound represented by the following formula (10).
  • the wet cake containing the compound represented by the formula (11) obtained in Synthesis Example 8 was dissolved in 240 mL of water, and 3/4 of the whole amount thereof was transferred to a 1-L beaker.
  • a 25% sodium hydroxide aqueous solution was added to the resultant aqueous solution to regulate the pH at 10.0 to 10.2, and the resultant was heated up to 60° C. 7 equivalents in total of propane sultone were added dropwise to the solution, and stirred at 60° C. for 6 hours. During this, the pH of the solution was held at 10.0 to 10.2 with a 25% sodium hydroxide aqueous solution.
  • the obtained reaction liquid was poured in 800 mL of methanol, and then, a deposited solid was filtration separated to thereby obtain a wet cake.
  • the wet cake was dissolved in 100 parts of a 25% sodium hydroxide aqueous solution, and poured in 800 mL of methanol, and then, a deposited solid was filtration separated to thereby obtain a wet cake. This operation was carried out twice in total.
  • the obtained wet cake was dissolved in 100 parts of water; and the pH was regulated at 10.0 by using a 35% hydrochloric acid and the resultant was heated up to 60° C. 4 equivalents of propane sultone were added dropwise thereto and stirred at 60° C. for 5 hours.
  • reaction liquid was poured in 800 mL of methanol and then, a deposited solid was filtration separated to thereby obtain a wet cake.
  • the wet cake was dried in a hot-air dryer at 80° C. to thereby obtain 56.6 parts of a heterocyclic compound of the present disclosure represented by the following formula (3-4).
  • the solubility to water of each heterocyclic compound (active material) obtained in Examples 16 to 21 was calculated from the absorbance.
  • the measurement of the absorbance used an ultraviolet-visible spectrometer (UV-1700, manufactured by Shimadzu Corp.). Solutions of known concentrations of a sample were prepared by using a standard buffer solution (manufactured by Fujifilm Wako Pure Chemical Corp., a neutral phosphate salt pH standard solution, pH: 6.86 (25° C.)), and the absorbances at the maximum absorption wavelength in the wavelength region of 300 nm to 550 nm were measured by the ultraviolet-visible spectrometer. A calibration curve was fabricated from the obtained absorbances and the concentrations.
  • the heterocyclic compound represented by the formula (3-1) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 8.
  • sodium iodide manufactured by Junsei Chemical Co., Ltd., first grade
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • An ion-exchange membrane (manufactured by Sigma-Aldrich Japan, Nafion(R) NRE-212) was used as a membrane, and carbon felts (manufactured by Toyobo Co., Ltd., AAF304ZS, 10 mm ⁇ 50 mm ⁇ 4 mm) were used as electrodes.
  • the carbon felts were each put in the hole of 10 mm ⁇ 50 mm of a silicon-made gasket (thickness: 3 mm), and these were assembled so as to make a current collecting plate/an electrode/a membrane/an electrode/a current collecting plate in this order.
  • the fabricated negative electrode electrolytic solution 8 and positive electrode electrolytic solution 8 were used as electrolytic solutions, to thereby fabricate a redox flow battery 8.
  • the positive electrode electrolytic solution 8 and the negative electrode electrolytic solution 8 of the redox flow battery 8 were circulated by peristaltic pumps piped and connected to outsides of the battery; and the test was carried out by using the multi-electrochemical measurement system (manufactured by Hokuto Denko Corp., HZ-Pro).
  • the solution volumes of the positive electrode electrolytic solution 8 and the negative electrode electrolytic solution 8 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.7 V.
  • FIG. 8 shows a charge/discharge curve until the fifth cycle of the redox flow battery 8. In the fifth cycle, the coulomb efficiency was 84%; the voltage efficiency, 92%; and the energy density, 1.04 Wh/L, thus attaining a good cycle characteristic.
  • the heterocyclic compound represented by the formula (3-2) was dissolved in a potassium chloride (manufactured by Junsei Chemical Co., Ltd., special grade) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 9.
  • potassium iodide manufactured by Junsei Chemical Co., Ltd., special grade
  • a potassium chloride manufactured by Junsei Chemical Co., Ltd., special grade
  • a redox flow battery 9 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 9 and the positive electrode electrolytic solution 9, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 9 and the negative electrode electrolytic solution 9 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.7 V.
  • FIG. 9 shows a charge/discharge curve until the fifth cycle of the redox flow battery 9. In the fifth cycle, the coulomb efficiency was 87%; the voltage efficiency, 88%; and the energy density, 1.08 Wh/L.
  • the heterocyclic compound represented by the formula (3-3) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 10.
  • sodium iodide manufactured by Junsei Chemical Co., Ltd., first grade
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • a redox flow battery 10 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 10 and the positive electrode electrolytic solution 10, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 10 and the negative electrode electrolytic solution 10 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.4 V and the lower limit voltage being set at 0.5 V.
  • FIG. 10 shows a charge/discharge curve until the fifth cycle of the redox flow battery 10. In the fifth cycle, the coulomb efficiency was 84%; the voltage efficiency, 82%; and the energy density, 0.46 Wh/L.
  • the heterocyclic compound represented by the formula (2-1) was dissolved in a potassium hydroxide (manufactured by Junsei Chemical Co., Ltd., special grade) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 11.
  • potassium ferrocyanide manufactured by Kanto Chemical Co., Inc., special grade
  • a potassium hydroxide manufactured by Junsei Chemical Co., Ltd.
  • a redox flow battery 11 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 11 and the positive electrode electrolytic solution 11, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 11 and the negative electrode electrolytic solution 11 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.3 V and the lower limit voltage being set at 0.7 V.
  • FIG. 11 shows a charge/discharge curve until the fifth cycle of the redox flow battery 11. In the fifth cycle, the coulomb efficiency was 88%; the voltage efficiency, 92%; and the energy density, 0.81 Wh/L.
  • the heterocyclic compound represented by the formula (3-4) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 12.
  • sodium iodide manufactured by Junsei Chemical Co., Ltd., first grade
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • a redox flow battery 12 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 12 and the positive electrode electrolytic solution 12, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 12 and the negative electrode electrolytic solution 12 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.6 V and the lower limit voltage being set at 0.5 V.
  • FIG. 12 shows a charge/discharge curve until the fifth cycle of the redox flow battery 12. In the fifth cycle, the coulomb efficiency was 87%; the voltage efficiency, 91%; and the energy density, 0.85 Wh/L.
  • the heterocyclic compound represented by the formula (3-5) was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 13.
  • sodium iodide manufactured by Junsei Chemical Co., Ltd., first grade
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • a redox flow battery 13 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 13 and the positive electrode electrolytic solution 13, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 13 and the negative electrode electrolytic solution 13 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.6 V and the lower limit voltage being set at 0.5 V.
  • FIG. 13 shows a charge/discharge curve until the fifth cycle of the redox flow battery 13. In the fifth cycle, the coulomb efficiency was 90%; the voltage efficiency, 86%; and the energy density, 0.94 Wh/L.
  • Sodium 9,10-anthraquinone-2-sulfonate was dissolved in a sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 14.
  • sodium iodide manufactured by Junsei Chemical Co., Ltd., first grade
  • a sodium chloride manufactured by Tokyo Chemical Industry Co., Ltd., purity: >99.5%
  • a redox flow battery 14 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 14 and the positive electrode electrolytic solution 14, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 14 and the negative electrode electrolytic solution 14 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.5 V.
  • FIG. 14 shows a charge/discharge curve until the fifth cycle of the redox flow battery 14. In the redox flow battery 14, the active material concentration was insufficient and good charge/discharge characteristic was not attained.
  • a redox flow battery 15 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 15 and the positive electrode electrolytic solution 15, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 15 and the negative electrode electrolytic solution 15 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.5 V.
  • FIG. 15 shows a charge/discharge curve until the fifth cycle of the redox flow battery 15.
  • the coulomb efficiency was 71%; the voltage efficiency, 76%; and the energy density, 0.01 Wh/L.
  • the redox flow battery 15 was inferior in the cycle characteristic and the energy density to the redox flow batteries fabricated in the other Examples.
  • Potassium 9,10-anthraquinone-1,8-disulfonate was dissolved in a potassium chloride (manufactured by Junsei Chemical Co., Ltd., special grade) aqueous solution (1.0 mol/L) to attain 0.1 mol/L to thereby fabricate a negative electrode electrolytic solution 16.
  • potassium iodide manufactured by Junsei Chemical Co., Ltd., special grade
  • a potassium chloride manufactured by Junsei Chemical Co., Ltd., special grade
  • a redox flow battery 16 was fabricated as in Example 22, except for altering the negative electrode electrolytic solution 8 and the positive electrode electrolytic solution 8 in Example 22 to the negative electrode electrolytic solution 16 and the positive electrode electrolytic solution 16, respectively.
  • the charge/discharge test was carried out by the same operation as in Example 22.
  • the solution volumes of the positive electrode electrolytic solution 16 and the negative electrode electrolytic solution 16 were 20 ml and 6 ml, respectively; and the charge/discharge test was carried out at a constant current of 105 mA and with the upper limit voltage being set at 1.5 V and the lower limit voltage being set at 0.7 V.
  • FIG. 16 shows a charge/discharge curve until the fifth cycle of the redox flow battery 16. In the redox flow battery 16, the active material concentration was insufficient and good charge/discharge characteristic was not attained.
  • Example 22 redox flow formula (3-1) 1.10 84 92 1.04 battery 8
  • Example 23 redox flow formula (3-2) 1.06 87 88 1.08 battery 9
  • Example 24 redox flow formula (3-3) 0.98 84 82 0.46 battery 10
  • Example 25 redox flow formula (2-1) 0.94 88 92 0.81 battery 11
  • Example 26 redox flow formula (3-4) 1.09 87 91 0.85 battery 12
  • Example 27 redox flow formula (3-5) 1 90 86 0.94 battery 13 Comparative redox flow 9,10-anthraquinone-2- N/A N/A N/A Example 1 battery 14 sulfonic acid (Na) Comparative redox flow 9,10-anthraquinone-1,5- 0.84 71 76 0.01
  • Example 2 15 disulfonic acid (Na) Comparative redox flow 9,10-anthraquinone-1,8- N/
  • An active material containing the heterocyclic compound of the present disclosure, and an electrolytic solution and a redox flow battery containing the active material can provide the redox flow battery with a high energy density and a good cycle characteristic.
  • the electrolytic solution of the present disclosure which is an aqueous electrolytic solution, is safer and easier to handle as compared with organic solvent-based electrolytic solutions, enabling the electrolytic solution to be applied to a wide range of uses.

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